Ventilated furnace casing construction



'June 9, 1936. J. w. NORRIS VENTILATED FURNACE CASING CONSTRUCTION Filed March 12, 1934 Patented June 9, 1936 VENTILATED FURNACE CASING CONSTRUCTION John W. Norris, Marshalltown, Iowa, assignor to Lennox Furnace Company,

Iowa, a corporation Marshalltown,

Application March 12, 1934, Serial No. 715g120 2 Claims. (Cl. 126--110) The object of my invention is to provide a ventilated furnace casing construction whichis simple, durable and comparatively inexpensive to manufacture.

A further object is to provide a ventilated furnace casing construction for the purpose of reducing the heat radiation from the furnace casing, this being especially desirable in modern furnace rooms where the space is restricted and consequently becomes excessively heated if there is any marked radiation from the casing of the furnace.

Still a further object is to provide a furnace construction in which both an inner casing and an outer casing are employed with the greater portion of the incoming air passing upwardly between the furnace body and the inner casing and being heated thereby, a small quantity of the air passing upwardly between the inner casing and the outer casing and heated only by the heat from the inner casing instead of the direct heat of the furnace body, so that it is much cooler than the air inside of the inner casing, thus keeping the outer casing much cooler than when a single casing is used surrounding the furnace.

Still a further object is to provide for circulation of the cooler air between the inner and outer casings without any additional apparatus and without wasting any of the heat absorbed by this air, such means being in the form of openings which permit the warmed air from between the casings to re-enter the inner casing and thoroughly mix with the hot air therein, a. restricted cone-shaped upper end being provided on the inner casing for this purpose so that the air is thoroughly mixed as it enters a plenum chamber surmounting the inner and outer casings.

Still a further object is to so construct the outer and inner casings that the incoming cold air either from a blower or a gravity cold air shoe can be properly divided and introduced to the space both inside and outside the inner casing without any complicated construction or inand Figure 2 is a horizontal sectional view on the line 2- -2 of Figure 1.

On the accompanying drawing, I have used the reference character A to indicate generally a furnace body, B an inner casing and C an outer casing. The furnace body A may be of any approved construction, it being illustrated on the drawing as a cylindrical casing having a fire box ID, ash pit l2 and chimney connection l4. A radiator is indicated-at IS.

The inner casing B comprises a cylinder l8 terminating at its upper end in a cone-shaped portion 20 and a sleeve 22. The sleeve 22 enters a plenum chamber 24 from which hot air pipes 26 lead to the various rooms to be heated.

The outer casing C comprises a rectangular portion 28 terminating in a cone-shaped portion 30 connected with the plenum chamber 24. A partition 32 separates the upper end of the outer casing C from the plenum chamber.

A cold air blower is indicated at 34. It has a cold air outlet 36 connected with the outer casing C. A blower is not essential-for my invention as gravity fed cold air may be supplied to the outlet 36 instead of the blower 34 being used.

The inner casing B is provided with an air reception opening38. It is of substantially the same size and shape as the cold air outlet 36 so that most of the cold air therefrom jumps the gap between the discharge end of the outlet 36 and opening 38 and enters the opening.

The inner casing B is provided adjacent its lower end with a series of enlarged outlet openings 4!). At its top, in the cone-shaped portion 20 thereof, it is provided with inlet openings 42 which are somewhat restricted.

These openings play an important part in the operation of my ventilated casing.

Practical operation In the operation of the furnace disclosed, most of the air is forced from the outlet 36 into the space between the furnace body A and the inner casing B by jumping the gap between the outlet 36 and the opening 38 in the inner casing. This air comes in intimate contact with the furnace body A and the radiator It for the purpose of heating the air before it enters the plenum chamber 24. As it enters the plenum chamber, its velocity is increased by the restricted cone-shaped portion 20 of the inner casing, the purpose of which will hereinafter appear.

Part of the air entering the inner casing flows outwardly through the enlarged openings 40. This air. is indicated by dotted line arrowsinstead of solid line arrows which indicate the air heated by the furnace body A and the radiator l6. Also, some of the air, in jumping from the outlet 35 to the opening 38, will strike the edges'of the opening and flow upwardly between the casings B and C.

This air flowing upwardly, as indicated by the dotted line arrows, re-enters the inner casing through the restricted openings 42, the size and number of these openings predetermining the proportion of air flowing upwardly between the casings B and C.

The air between the furnace body .and the inner casing will become hotter than in ordinary furnaces having but one casing because of the air flowing upwardly between the casings B and C becoming warmer than the atmosphere surrounding the casing C. The air between the casings will be cooler than the air within the casing of a furnace having but a single casing and therefore there will be less radiation to the surrounding atmosphere with a consequent increase in efficiency and decrease in undesirable high temperature of the furnace room.

To prevent any possibility of the cooler air from between the casings B and C flowing to one room and for the purpose of insuring that every portion of the air flowing from the plenum chamber 24 is of the same temperature, the openings 42 are located so that the air indicated by the dotted line arrows enters the air stream indicated by the full line arrows at the point where its velocity is greatest. This churns and intermixes the air, so that although slightly reducing the temperature of the air indicated by the full line arrows, the temperature is even throughout and for the same fuel consumption is higher than when a single casing is used.

The result of my construction is very satisfactory for a forced air heating installation. The outer casing C is maintained cool during even the heaviest firing of the furnace, yet the air to be heated is held in intimate contact with the furnace body and the radiator l6. These are vital features of any correct forced air furnace where great efficiency is desired.

By providing the outer casing C surrounding the inner casing B, I have provided a form of insulation for the casing B. The air between the casings has the effect of wiping the heat from the casing B, and in so doing, accomplishes an increase in overall operating efficiency of the furnace because this heat, which would normally be lost from the casing B, tempers the air flowing between the casings and the tempered air flows back into the main hot air stream.

It is obvious that this is a desirable construction as insulation such as rock wool or asbestos is impractical for hot air furnaces, although it is satisfactory for boilers and the like because they develop less temperature than the hot air casing surrounding a furnace body.

My construction also enables the use of a rec- 5 tangular outer casing without forming undesirable dead air pockets as when only a single casing is used, the dead air pockets in the double casing being immaterial as this is cooler air and not the air to be circulated and directly heated by the furnace.

Some changes may be made in the construction and arrangement of the parts of my device without departing from the real spirit and purpose of my invention, and it is my intention to cover by my claims, any modified forms of structure or use of mechanical equivalents, which may bereasonably included within their scope.

I claim as my invention:

1. In a furnace construction, a furnace body, an inner casing therearound and spaced therefrom, a plenum chamber above said inner casing, the upper portion of said inner casing being restricted before communicating with said plenum chamber, the restricted portion being pitched upwardly and inwardly, an outer casing surrounding said inner casing and spaced therefrom, a cold air inlet connected with said outer casing adjacent the bottom thereof, an opening in said inner casing arranged in registry with said cold air inlet, a series of openings in said inner casing adjacent the bottom thereof for admitting air from between the inner casing and the furnace body to the space between the inner casing and the outer casing and restricted openings in the pitched portion of said inner casing in the restricted portion thereof to induce mainly by venturi action, flow of air from between said inner casing and said outer casing to the space within said inner casing after such air travels up through the space between said inner casing and said outer casing from the bottom to the top thereof.

2. A furnace construction comprising an outer casing having a single cold air inlet, a blower having its outlet connected therewith, an inner casing having a cold air inlet registering therewith and cold air outlets to the space between said casings, a furnace body within said inner casing, said inner casing also having a coneshaped upper end terminating in a hot air outlet over the furnace body and tempered air inlets in said cone-shaped upper end and adjacent said hot air outlet for passing air which flows through said cold air outlets and enters the space between said casings and then flows from between said casings through said tempered air outlets and into said inner casing above the furnace body.

JOHN W. NORRIS. 

